Is an announcement (once the downgrade is done) to fedora-devel-list
sufficient, or are there any other appropriate mailing lists deemed
relevant?

The downgraded package was built and released yesterday, but effectively
never made it into the repo because the existing broken package has a
higher EVR. Once the existing package is nuked, will I need to resubmit
a build request for the downgrade package, and will I need to bump the
release to avoid an "invalid build" since it's already been built and
"released" before?